Bearing for vacuum tube work



Sept. 9, 1947. s. F, ESSIG 2,427,203

BEARING FOR VACUUM TUBE WORK 7 Filed May 14, 1945 INVENTOR SANFORD EESSIG ATTORNEY Patented Sept. 9, 1947 BEARING FOR, VACUUM TUBE WORKSanford F. Essig, Fort Wayne, Ind., assignor to Farnsworth Televisionand Radio Corporation, a corporation of Delaware Application May 14,1945, Serial No. 593,747

Claims. (Cl. 308241) This invention relates generally to electrodesupports for vacuumtubes, and more particularly relates to devices formovably supporting electrodes in glass supports.

It is frequently desirable to supply mechanical motion to certainelectrodes of a vacuum tube. Thus, an unbalanced wheel may be turned bythe action of gravity or a magnetic armature may be rotated by anexternal magnetic field thereby to move an electrode. In this manner itis possible to exchange, for example, in a cathode ray tube, oneelectrode having a large aperture for another electrode having a smallaperture in order to vary the cross-sectional area of an electron beam.In certain types of X-ray tubes it is necessary to rotate the anode inorder to presenta different area to the electron beam to preventoven-heating of the anode. It may also. be desired to change theelectron emission of a cathode in a vacuum tube or similar device bymoving a shield in front of the cathode to. obscure a larger or smallerportion of the electron beam.

- It is conventional practice to provide most types of vacuum tubes witha glass envelope. Thus, the

problem arises 'of movably mounting an electrode support which usuallyconsists of metal in the glass envelope of a vacuum tube. However, as

is well known, glass wets metals and, therefore,

forms a bond with the metal. Hence, it is very desirable to provideapparatus for movably suppoiting a metallic electrode in a glassenvelope.

It is an object of the present invention, therefore, to provides. novel,movable electrode support suitable for use in vacuum tubes and a methodof manufacturingthe same.

A further object of the invention is to provide a bearing adapted to bemounted in a glass support.

In accordance with the present invention, there is provided. apparatusfor movably supporting an electrode in an evacuated vessel comprising aglass envelopaa metallic electrode support, a coating of lubricant filmon a portion of the electrode support and a metallic sleeve in intimatecontact with the lubricant film and a portion of the glass envelope.

For a better understanding of the invention, together with other andfurther objects thereof, reference is made to the following description,taken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

In the accompanying "drawing, Fig. 1 is a sectional view of two bearingsembodying'the present invention and mounted in a glass envelope, whilelit , shown by way of illustration and may be used for securing theretothe elements such, for example, as electrodes which it is desired torotate.

Bearing 5 without its glass support 3 is shown on enlarged scale in Fig.2. In. accordance with the present invention, the free end portion ofrod '6 is coated with a film ll of a suitable lubrL cant of low vaporpressure such, for example, as graphite or certain metals includingsilver or barium. Preferably, film Ii consists of graphite which is agood lubricant and has a low vapor pressure. Graphite film ll may beapplied as an aqueous suspension of graphite such as Aquadag. Theaqueous graphite suspension may then be 5 dried, for instance, byheating rod 6, to form graphite film If.

Since glass can not be made to wet graphite film ii, it may be coatedwith a metal to form a tight fitting sleeve i2, the coating beingpreferably effected by plating graphite film H with a metal. The metalof which sleeve i2 consists should have the same thermal coeilicient ofexpansion as glass support 3. Thus, when glass supports 2 and 3 consistof lead glass or lime glass, that is of soft glass, metallic sleeve l2may, for instance, be made of platinum or Dumet which is a co per-cladnickel-copper alloy. The

thermal .coeflicient of expansion of tungsten. matches that of Pyrex aswell as Nonex which are both hard glasses. Kovar or Fernico and similariron-alloy metals may be used in connection with a special seal glasssold in the trade under the name 0127052 glass.

After graphite film II has been plated with metal to form sleeve or filml2, both metallic sleeve i 2 and its glass support such as 3 are heateduntil the glass wets metallic sleeve l2. metallic sleeve i2 is embeddedin hot glass sup- Now port 3. After glass support 3 and metallic sleeveV! have cooled the glass forms a bond with metallic sleeve i2. Metallicrod 6 will now turn freely in its metallic sleeve l2, while graphitefilm ll acts as a lubricant. Circular grooves i and 8, which preferablyare provided in rod 6, prevent rod 6 from moving axially in itsbearings. It is also feasible to coat only circular grooves I and 8 withgraphite film II and metallic sleeve H in which case grooves I and 8provide the actual bearing. Bearing 4 may bemanufactured in the samemanner as bearing 5.

A bearing of the type described will operate as well in a high vacuum asunder atmospheric pressure. Lubricant film ll preferably consists ofgraphite which has a very low vapor pressure and thus can notcontaminate the vacuum tube. If graphite film ll would be embeddeddirectly in glass; the glass would not wet the graphite and hence aclose fit could not be obtained.

While there' has been described what is at present considered thepreferred embodiment of the invention, it will be obvious to thoseskilled in the art that various changes and modifications k maybe madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover allsuch changes and modificationsas fall within the true spirit and scope of the invention.

What is claimed is:

1. Apparatus for movably supporting an electrode in an evacuated vesselcomprising a glass envelope, a metallic electrode support, a coating oflubricant film on a portion of said support, and a metallic sleeve inintimate contact with said film and a portion of said glass envelope.

2. Apparatus for movably supporting an electrode in an evacuated vesselcomprising a glass envelope, a metallic electrode support havingaportion provided with a circular groove, a coating of graphite film onsaid portion and said groove,

and a metallic sleeve in intimate contact with.

said film and a portion of aid glass envelope.

3. Apparatus for movably supporting an electrode in an evacuated vesselcomprising a glass envelope, a metallic electrode support, a coating ofgraphite film on a portion of said support, and

- '4 a metallic sleeve in intimate contact with said film and a portionof said glass envelope, said metallic sleeve and said glass envelopebeing chosen to have'substantially the same thermal coefiicient ofexpansion.

4. Apparatus for movably supporting an electrode in an evacuated vesselcomprising a glass envelope, a metallic electrode support having an endportion provided with a circular groove, a coating of graphite film onsaid groove, and a metallic film in intimate contact with said graphitefilm and a portion of said glass envelope, said metallic film and saidglass envelope being chosen to have substantially the same thermalcoefiicient of expansion.

5. The method of movably supporting a metallic electrode support in anevacuated glass envelope which comprises-the steps of coating a portionof said support with an aqueous suspension of graphite to form agraphite film, selecting a' metal having the same thermal coefficient ofexpansion as said glass envelope, plating said graphite film with saidselected metal to form a metallic sleeve, heating said metallic sleeveand a portion of said glass envelope until said glass wets said metallicsleeve, and embedding said metallic sleeve in said portion of 'saidglass'envelope to form a bond therewith.

SANFORD F. ESSIG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number 7, Name Date 1,016,320 Burnside Feb. 6,1912 2,364,290 Hanson Dec. 5, 1944 2,315,280 Skehan et al Mar. 30, 1943

